There comes a point when sales for a particular version drop to a level that means it isn't economically viable to keep developing for it. That happened to me when downloads of the XP version of Plan-G dropped below 1% of Win7/10 downloads. For me it's less about money, but when you're depending on sales ROI for income, sometimes you have to make the hard decisions, and it looks like that's happened with CS.
Hopefully their 64-bit products will go from strength to strength.